1. Field of the Invention
This invention relates to a developer amount indicating method, an electrophotographic image forming apparatus and a process cartridge.
Here, an electrophotographic image forming apparatus is an apparatus for forming an image on a recording medium by the use of an electrophotographic-image-forming process. It covers, for example, an electrophotographic copier, an electrophotographic printer (such as an LED printer or a laser beam printer), an electrophotographic facsimile apparatus and an electrophotographic word processor.
Also, here, a process cartridge refers to at least one of charging means, developing means and cleaning means as process means and an electrophotographic photosensitive member integrally made into a cartridge, which is detachably mountable to the main body of the electrophotographic image forming apparatus. Or it refers to developing means as process means and an electrophotographic photosensitive member integrally made into a cartridge, which is detachably mountable to the main body of the electrophotographic image forming apparatus.
2. Related Background Art
In an electrophotographic image forming apparatus, there has heretofore been adopted a process cartridge system whereby an electrophotographic photosensitive member and process means acting on the electrophotographic photosensitive member are integrally made into a cartridge which is detachably mountable to the main body of the electrophotographic image forming apparatus. According to this process cartridge system, the maintenance of the apparatus can be done by a user himself without resorting to a serviceman and therefore, the operability of the apparatus can be markedly improved. So, this process cartridge system is widely used in electrophotographic image forming apparatus.
In the image forming apparatus of such a process cartridge type, as a standard for the user to effect the interchange of the process cartridge, there is the function of detecting that the remaining amount of developer in a developer container provided in the process cartridge has assumed a predetermined value or less, and informing the user of it.
Also, in order to improve the convenience to the user, the function of successively detecting the remaining amount of developer and informing the user of the remaining amount of developer by a gauge corresponding to the amount of developer as shown, for example, in FIG. 18 of the accompanying drawings has been put into practical use. In a developer remaining amount indicator 40 shown in FIG. 18, the user is informed of the remaining amount of developer by what portion of an indicating portion (gauge) 42 provided with a scale 42a from "Full" to "Empty" is pointed to by a pointer 41 moving in conformity with the remaining amount of developer.
In recent years, a plurality of types of process cartridges differing from one another in the amount of developer filling a developer container have been prepared so that the user can select them. Image forming apparatuses capable of mounting such a plurality of types of process cartridges have been commercialized.
Usually, when the amount of developer in a process cartridge is to be detected, the absolute amount of developer is detected. Therefore, it is conceivable that there is a possibility that a distinction cannot be made between a case where a new process cartridge having a small amount of developer filling a developer container (hereinafter referred to as the "low capacity process cartridge") has been mounted and a case where a process cartridge having a large in the amount of developer filling a developer container (hereinafter referred to as the "high capacity cartridge") that has decreased by consumption has been mounted.
In the image forming apparatus on which such a plurality of types of process cartridges are mounted, when the user is informed of the remaining amount of developer by the conventional gauge system shown in FIG. 18, the following problems can occur. When for example, the position of "Full" is adjusted so as to indicate the fullness of a small developing capacity cartridge, if the high capacity cartridge is mounted, the pointer 41 continues to stay at the position of "Full" in the gauge 42 until the developer is consumed up to an amount corresponding to the fullness of the low capacity cartridge with the developer. Accordingly, the problem occurs that in the meantime, the amount of developer cannot be indicated successively.
Also, when the position of "Full" shown in FIG. 18 is adjusted so as to indicate the fullness of the high capacity cartridge with the developer, if a low capacity cartridge is mounted, it would occur that in spite of the cartridge being new, the pointer 41 points to a position less than the "Full" in the gauge 42.